JPH0962034A - Production of electrophotographic toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain such an electrophotographic toner that electrification control can be easily done for a positive electrification toner by using the same start material as for the production of a negative electrification toner in the same granulation process. SOLUTION: This electrophotographic toner is produced in the following processes. In the first process, a coloring agent, monothylene-type polymerizable monomers containing an acid group and a dispersion stabilizer as the essential components are polymerized in a liquid medium which does not dissolve the monomers in the presence of a polymn. initiator which is insoluble with the liquid medium and is soluble with the monomer to obtain a dispersion liquid of toner particles which does not dissolve in the liquid medium and consists of a polymer of the monomers including the coloring agent. In the second process, the acid group in the polymer is neutralized by adding a nigrosine compd. In the third process, the liquid medium is removed from the dispersion liquid and the toner is dried. By this method, a positive electrification toner can be produced in the same granulating process as for a negative electrification toner without changing any granulating conditions for polymn. so that changing of kinds of toners can be efficiently done. Thus, the productivity of the toner can be largely improved.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a dry toner composition for developing an electrostatic latent image in electrophotography, electrostatic recording, electrostatic printing and the like.

[0002]

2. Description of the Related Art In electrophotography, dry developers are roughly classified into one-component developers using a toner itself in which a colorant is dispersed in a binder resin and two-component developers in which the toner and a carrier are mixed. can do.

In any case, when copying, the electrostatic latent image formed on the photoconductor is developed with these developers, and the toner powder imaged on the photoconductor is transferred to a transfer material such as paper or sheet. The image is fixed using heat, pressure, etc. to obtain a permanent image. At that time, in order to obtain a permanent image with sufficient image density and high resolution, it is necessary to adhere a predetermined amount of toner powder to the electrostatic latent image formed on the photoconductor faithfully to the latent image. .

Normally, the polarity of the electrostatic latent image formed on the photosensitive member is positive or negative depending on the type of the photosensitive member and the difference in the developing system. Is also required to have a charging property with a negative or positive polarity opposite to the electrostatic latent image on the photoconductor.

In recent years, a polymerization method toner has been attracting attention as a toner whose usage amount is increasing more and more as an image forming material for a copying machine, a laser printer and the like.

In the conventional toner manufacturing method, a mixture of a binder resin and a coloring agent is kneaded while being melted by a heating mixer, cooled, and then mechanically pulverized and finely pulverized by a pulverizer such as a jet mill. A method is generally used in which toner particles are classified to obtain toner particles, and if necessary, an external additive is mechanically mixed (dry method), and the particle shape is an angular polyhedral shape like crushed ice. It was characterized by that.

On the other hand, a toner produced by a polymerization method typified by suspension polymerization or emulsion polymerization is completely different from a conventional mechanical pulverization method, and for example, is mixed with a binder resin in the presence of a colorant in an aqueous medium. This is a method of chemically reacting a monomer to be synthesized to synthesize a binder resin and, at the same time, granulating particles containing a colorant, and toner particles are manufactured in one step.

A major characteristic of this polymerization toner is
It is difficult to obtain by a dry process, and it is possible to make a toner shape substantially spherical and to easily manufacture a uniform particle toner having a sharp particle size distribution. Such a spherical toner offers the advantage of being able to design a small particle size toner having excellent powder flowability, and is expected to develop into a high-performance toner that matches the market demand for high image quality and high resolution. There is.

[0009]

One of the common problems of toners produced by polymerization utilizing emulsion polymerization or suspension polymerization is that the stable positive or negative toners obtained by conventional mechanically pulverized toners are used. However, there is a problem in that it is difficult to impart the charging characteristics of 1. to the toner particles. Specifically, in the polymerization process, since the toner particles are granulated in a liquid medium, if the type of the charge control agent changes, the dispersibility of each component in the aqueous medium may differ, or the reaction of the monomer There is a problem in that the granulation of the toner particles itself becomes difficult because the speed is affected, and further it is not possible to obtain uniform colorant-dispersed particles. Therefore, it is necessary to individually devise to manufacture positively chargeable toner or negatively chargeable toner,
There was a problem that the productivity was inferior when there were various kinds of products.

In view of the above-mentioned circumstances, the present invention provides a method for producing a polymerized toner which can easily perform charge control for achieving positive chargeability and can efficiently cope with product type switching in multi-product production. More specifically, it is to provide a method for producing a dry toner having a structure in which a nigrosine compound is ionically attached to an anionic functional group that is an acidic group on the surface of toner particles obtained by suspension polymerization or emulsion polymerization, Polymerization that uses the same starting material as the negatively chargeable toner and can easily produce positively chargeable toner in the same granulation process. Controlling from negative chargeability to positive chargeability by a simple operation It is an object of the present invention to provide a method for producing an electrophotographic toner of the production method.

[0011]

As a result of intensive studies, the inventors of the present invention have solved the above problems. That is, the present invention is as follows.

A colorant, an acid group-containing monoethylenically polymerizable monomer, and a dispersion stabilizer are contained as essential components in a liquid medium in which the monomer is insoluble, insoluble in the liquid medium, and in the unit amount. Polymerization in the presence of a body-soluble polymerization initiator to obtain a dispersion liquid of the toner particles insoluble in the liquid medium, which is a polymer of the monomer including a colorant, and a nigrosine compound Is added to neutralize the acid groups in the polymer, and then a third step of removing the liquid medium from the second step and drying the electrophotographic toner (first invention).

A colorant and a monoethylenically polymerizable monomer containing an acid group are used as essential components, and they are ultrasonically dispersed to obtain a monomer-insoluble liquid medium which is insoluble in the liquid medium and Polymerization is performed in the presence of a polymerization initiator soluble in the monomer to obtain a dispersion liquid of the toner particles insoluble in the liquid medium, which is composed of a polymer of the monomer including a colorant. And a nigrosine compound to neutralize the acid groups in the polymer, and then a third step of removing the liquid medium and drying it (second invention).

A colorant, a monoethylenically polymerizable monomer having an acid group, and an emulsifier are used as essential components, and polymerization is carried out in an aqueous medium in the presence of a water-soluble polymerization initiator to include the colorant. A first step of obtaining a dispersion of the toner particles insoluble in the aqueous medium, which comprises a polymer of the monomer, a second step of adding a nigrosine compound thereto to neutralize the acid groups in the polymer, and then A method for producing an electrophotographic toner comprising a third step of removing an aqueous medium and drying (third invention).

The toner particles obtained by the production method of the present invention are particles containing a colorant and a binder resin produced by radical polymerization of an ethylenically polymerizable monomer as essential components, and are colored. The binder resin containing the agent dispersed therein contains a functional group having anion forming ability such as a carboxyl group, a phosphoric acid group and a sulfonic acid group, that is, an acid group, and a part of the acidic group is present on the toner particle surface. It is exposed to and is partially of an acidic group, which is neutralized with a nigrosine compound.

A toner particle containing such a colorant, which is anion-formed, that is, an acid group is neutralized with a nigrosine compound, and a binder resin having a part of its functional group exposed on the surface of the particle is a toner particle. After polymerizing by applying a conventionally known suspension polymerization method or emulsion polymerization method using an ethylenically unsaturated monomer containing, the acid group is neutralized in an optional step thereafter, It can be obtained relatively easily by applying a known suspension polymerization method or emulsion polymerization method.

Specifically, for example, in the presence of a dispersion stabilizer or an emulsifier, a colorant and a reactive monomer capable of forming a binder resin are suspended or emulsified and dispersed in a liquid medium to prepare a polymerization initiator. In the presence of the above, the polymerization reaction by radical polymerization is carried out with stirring to obtain a spherical aqueous dispersion of toner particles in which a colorant is encapsulated in a binder resin. The definitions of suspension polymerization and emulsion polymerization are given in the Chemical Dictionary (Morikita Publishing).

A colorant, an ethylenically polymerizable monomer containing an acid group, and a dispersion stabilizer are essential components in a liquid medium in which the monomer is insoluble and insoluble in the liquid medium. Is polymerized in the presence of a soluble polymerization initiator to obtain a dispersion liquid of the toner particles insoluble in the liquid medium, which is composed of a polymer of the monomer including a colorant, or a colorant and an acid group. As an essential component with an ethylenically polymerizable monomer containing, they are mixed or dispersed by ultrasonic waves, using a dispersion stabilizer as needed, in the monomer-insoluble liquid medium, the liquid medium Polymerization is performed in the presence of a polymerization initiator insoluble in and soluble in the monomer to obtain a dispersion liquid of the toner particles insoluble in the liquid medium, which is composed of a polymer of the monomer including a colorant. The above is the method for producing a toner particle dispersion liquid by suspension polymerization in the present invention.

On the other hand, a colorant, an ethylenically polymerizable monomer containing an acid group, and an emulsifier are used as essential components, and polymerization is carried out in an aqueous medium in the presence of a water-soluble polymerization initiator to obtain the colorant. Obtaining the dispersion liquid of the toner particles insoluble in the aqueous medium, which is composed of the polymer of the above-mentioned monomers, is the method for producing the toner particle dispersion liquid by emulsion polymerization in the present invention.

Examples of the monoethylenically polymerizable monomer having an acid group include acrylic acid, methacrylic acid,
Crotonic acid, itaconic acid, maleic acid, fumaric acid, itaconic acid monobutyl, maleic acid monobutyl, acid phosphooxyethyl methacrylate, acid phosphooxypropyl methacrylate, 3-chloro-2-acrylamido-2-methylpropanesulfonic acid, 2-sulfo Examples thereof include ethyl methacrylate, and these may be used alone or in combination of two or more kinds.

In the present invention, it is possible to use only at least one kind of monomer selected from the above-mentioned monomers, but in order to improve various properties as a toner, a monomer usually containing the above acid group is used. By copolymerizing an ethylenically polymerizable monomer with another radically polymerizable monomer, a liquid medium containing an acid group such as a carboxyl group, a phosphoric acid group or a sulfonic acid group on the particle surface is formed. It may be a dispersed toner particle dispersion. The compounding ratio of the acid group-containing monomer is 2 to 30% by weight, preferably 10 to 30% by weight based on all the reactive monomers capable of forming the binder resin.
It is 20% by weight.

In the present invention, the charge control agent is not an essential component because the charge characteristics can be controlled by the acid group or the neutralized acid group in the binder resin.

Specific examples of the radically polymerizable monomer copolymerizable with the above-mentioned acid group-containing monomer include styrenes such as styrene, α-methylstyrene, chlorostyrene and vinylstyrene, ethylene, Propylene, butylene, isobutylene and other monoolefins, vinyl acetate,
Vinyl esters such as propion vinyl, vinyl butyrate, vinyl benzoate, methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, phenyl dodecyl acrylate, phenyl methacrylate, methyl methacrylate,
Ethyl methacrylate butyl methacrylate, α-methylene aliphatic monocarboxylic acid esters such as dodecyl methacrylate, ethylene glycol monoacrylate, propylene glycol monoacrylate, glycol mono (meth) acrylic acid ester such as tetramethylene ether glycol monoacrylate, Acrylic monomers such as vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether, vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl propenyl ketone, and the like, and these may be used alone or in combination of two or more. It can be used in combination.

The monomer composition of the binder resin is prepared so that the glass transition temperature of the polymer is 40 to 90 ° C, preferably 50 to 80 ° C.

If desired, a small amount of a reactive monomer having two or more ethylenically unsaturated double bonds may be used in combination therewith. Examples of the reactive monomer having two or more ethylenically unsaturated double bonds include conjugated dienes such as butadiene and isoprene, divinylbenzene, di (meth) acrylate of bisphenol A alkylene oxide adduct, and trimethylolpropanetri (meta). A) acrylate, pentaerythritol tetra (meth) acrylate, and the like.

As the polymerization initiator used for obtaining such a polymer resin, of course, a usual oil-soluble or water-soluble one can be used. For example, benzoyl peroxide,
Various peroxides such as di-t-butyl peroxide, cumene hydroperoxide, t-butyl peroxide or 2-ethylhexanoate; or various azo such as azobisisobutyronitrile or azobisisovaleronitrile. A compound etc. can be mentioned.

In the suspension polymerization, a polymerization initiator insoluble in the liquid medium used in the polymerization and soluble in the monomer is selected and used as an essential component, and in the emulsion polymerization, a water-soluble polymerization initiator is selected as an essential component. used. The amount of the polymerization initiator used is not particularly limited, but is 0.01 to 5 parts by weight per 100 parts by weight of all the reactive monomers (total monomers).

The binder resin formed by polymerization can be arbitrarily adjusted depending on the polymerization conditions and the like, but it is preferable to prepare it so that the weight average molecular weight is 10,000 to 500,000.

As the colorant in the toner particles used in the present invention, known and commonly used colorants can be used. Specifically, for example, carbon black, magnetic powder, aniline blue, calcoil blue, chrome yellow, ultramarine. Blue, DuPont Oil Red, Quinoline Yellow, Methylene Blue Chloride, Phthalocyanine Blue,
Malachite Green Oxalate, Lamp Black, Rose Bengal, C.I. I. Pigment Red 122, C.I.
I. Pigment Yellow 97, C.I. I. Pigment Blue 15, ferrosoferric oxide, ferric oxide, iron powder, zinc oxide, selenium, etc. can be used, and they can be used alone or in combination of two or more.

In the present invention, the toner obtained may be magnetic toner particles in which magnetic fine particles are dispersed in a binder resin. As the magnetic substance fine particles, any ferromagnetic substance that is normally used can be used.

Specific examples of the magnetic material include magnetic metals such as iron, cobalt and nickel, alloys of these, metal oxides such as cobalt-added iron oxide and chromium oxide, Mn / Zn ferrite, Ni / Zn ferrite and the like. Various kinds of ferrite,
In addition to magnetite, hematite, etc., the surface of these, silane coupling agent, aluminum coupling agent,
Powders such as those treated with a surface treatment agent such as a titanium coupling agent or those coated with a polymer can be used.

When carbon black is used as the colorant, it is preferable to use basic carbon black because it is excellent in affinity with the binder resin and a toner having good charging characteristics can be obtained.

The weight ratio of the colorant and the binder resin is not particularly limited, but it is preferable that the colorant is 3 to 30% by weight when the total weight thereof is 100. . In each of the polymerizations of the present invention, the above range is obtained per 100 parts by weight of the monomer which constitutes the binder resin finally and which contains the acid group-containing monoethylenically polymerizable monomer as an essential component. It is better to prepare

In the first and second inventions, a water-soluble polymer compound is generally used as the dispersion stabilizer that can be used during suspension polymerization, and examples thereof include polyvinyl alcohol, polyvinylpyrrolidone, hydroxyethyl cellulose and carboxymethyl cellulose. , Cellulose gum, rumzan gum and the like.

Further, it is insoluble in water and has a particle size of 0.01 to 5 μm.
Inorganic fine powder of m can also be used as a suspension dispersion stabilizer, for example, tricalcium phosphate, talc, bentonite, kaolin, titanium oxide, alumina, zinc white, aluminum hydroxide, magnesium hydroxide, basic magnesium silicate, Examples thereof include titanium hydroxide, ferric hydroxide, barium sulfate, silica, magnesium carbonate, calcium carbonate and the like.

These dispersion stabilizers may be used alone or in combination of two or more. The amount used is usually 0.1 to 10 parts by weight per 100 parts by weight of all reactive monomers.

In the third invention, examples of the emulsifier that can be used during emulsion polymerization include anionic surfactants such as sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium dodecyldiphenyloxide disulfonate, and polyoxyethylene lauryl ether. , Nonionic surfactants such as polyoxyethylene ninyphenol ether, and the like. These may be used alone or in combination of two or more. The amount used is usually 0.01 to 5 parts by weight per 100 parts by weight of the total reactive monomers.

In suspension polymerization, a dispersion stabilizer may be used in combination with an emulsifier, or in emulsion polymerization, an emulsifier may be used in combination with a dispersion stabilizer. Further, a self-emulsifiable epoxy resin or a self-emulsifiable polyurethane resin can be used in place of the dispersion stabilizer or the emulsifier.

In carrying out the first to third inventions, if necessary, for example, dodecyl mercaptan, carbon tetrachloride,
A chain transfer agent such as thioglycolic acid, a reducing agent such as sodium acid sulfite, sodium thiosulfate and sodium metabisulfite, and a chelating agent such as sodium ethylenediaminetetraacetate may be used in combination therewith.

In the first invention, the acid group-containing monoethylenically polymerizable monomer, the colorant, the dispersion stabilizer and the liquid medium insoluble in the monomer, insoluble in the liquid medium and soluble in the monomer The polymerization initiator may be added at the same time, and the monomer droplets may be polymerized by stirring, but the acid group-containing monoethylenically polymerizable monomer and the colorant may be sufficiently prepared in advance with, for example, a ball mill or a colloid mill. And then add it to the liquid medium containing a polymerization initiator, a dispersion stabilizer, for example a homogenizer,
Stir with a rotor-stator mixer, static mixer, etc. to suspend the monomer droplets containing the acid group-containing monoethylenically polymerizable monomer in the liquid medium, and continue stirring to give the desired particle size. It is preferable to carry out the polymerization until the toner particles are formed. This suspension polymerization is suitable for obtaining micron-sized toner particles.

In the third aspect of the present invention, when toner particles having a submicron size are obtained, an acid group-containing monoethylenically polymerizable monomer, a colorant, an emulsifier and an aqueous medium, and a water-soluble polymerization initiator are added at the same time. The monomer droplets may be emulsified and dispersed in an aqueous medium and polymerized, but in the case of obtaining toner particles of micron size, an acid group-containing monoethylenic polymerizable monomer, an emulsifier, a water-soluble polymerization initiator And an aqueous medium are sufficiently mixed and emulsified and dispersed in advance and then polymerized to form primary particles, and then a coloring agent is added to the primary particles and stirred to allow the primary particles to be adsorbed and associated with the primary particles to contain a coloring agent. Secondary particles are formed, and the secondary particles are granulated by slowly aggregating the secondary particles so that the particles have a predetermined particle size, and the dispersion liquid is heated to a temperature equal to or higher than the glass transition temperature of the binder resin in the agglomerated particles. Fuse the interface between the secondary particles It is preferable to.

The suspension polymerization has the advantage that impurities are finally less likely to be included as compared with the emulsion polymerization because the particles are relatively large from the beginning and the polymerization is carried out in one step.

In addition, ultrasonic waves may be added, if necessary, in uniformly mixing or dispersing each material. As in the case of the second invention, when the first invention is modified so that the colorant and the monoethylenically polymerizable monomer containing an acid group are mixed by ultrasonic waves to carry out the polymerization, a dispersion stabilizer is particularly used. Is not necessary.

The ultrasonic wave has a frequency of 16000, for example.
A sound wave of c / sec or more can be used. Ultrasonic waves, for example
High frequency voltage is applied to the crystal unit, and the fundamental frequency or odd multiple
Can be easily obtained by resonating at the frequency
You. 10^Fivesec^-1In the case of, a magnetostrictive oscillator is often used.
Can be The characteristic of ultrasonic waves is that the frequency is large and therefore the wavelength
It develops due to its shortness and its extremely high strength.
Frequency of 10 for liquid ⁶sec^-1Strength 10 watt
/ Cm²When, the acceleration of medium particles is
10^Five-10⁶And bring about the effects of emulsification and dispersion.

Since ultrasonic waves are used in the second invention, the dispersion stabilizer is substantially unnecessary. However, when the dispersion stability is further improved without using the dispersion stabilizer, the above-mentioned monomer is It is also effective to use in combination a liquid medium having a relatively good affinity.

In the present invention, the liquid medium means water and / or an organic solvent which is in a liquid state at room temperature, while the aqueous medium contains water as a main component and, if necessary, an organic solvent. It means a liquid medium that may be used. The aqueous medium is
It is preferable that the composition is such that only water or an organic solvent is contained in an amount of 30% by weight or less.

As the liquid medium which can be used in carrying out the polymerization in the present invention, various aromatic hydrocarbons such as toluene, xylene or benzene as well as water such as distilled water and ion-exchanged water; methanol, ethanol,
Various alcohols such as propanol or butanol; Various ether alcohols such as cellosolve or carbitol; Various ketones such as acetone, methyl ethyl ketone or methyl isobutyl ketone; Various esters such as ethyl acetate or butyl acetate , Or butyl cellosolve acetate,
Examples include various ether esters.

In any of the polymerization methods, the core-
By employing a shell polymerization formulation, a power feed polymerization formulation, or a graft polymerization formulation, the chemical structure and layer structure of the particles can be varied. The reaction conditions in each of the suspension polymerization method and the emulsion polymerization method of the above inventions are not particularly limited, and in each case, the reaction temperature is usually from room temperature to 80 ° C. for 15 minutes to 24 hours.

In obtaining the aqueous dispersion of toner particles used in the present invention, an auxiliary agent such as wax or a charge control agent may be added, if desired, in any step of its production.

Examples of the auxiliaries include waxes such as polyethylene wax, polypropylene wax and paraffin wax, metal soaps, lubricants such as zinc stearate,
Alternatively, an abrasive such as cerium oxide or silicon carbide, a copper phthalocyanine, perylene, quinacridone, an azo pigment, an azo metal-containing dye, a charge control agent such as an azochrome complex, etc. may be mentioned.

Each first of the first invention, the second invention or the third invention
In the step, in the toner particle dispersion liquid containing the binder and the colorant, which are obtained as described above and which are composed of the polymer of the ethylenically polymerizable monomer having an acid group, as a second step, A nigrosine compound is added to neutralize the acid groups represented by the carboxyl group, phosphoric acid group and sulfonic acid group in the polymer, particularly the acid groups exposed on the surface of the toner particles. At this time, stirring is usually carried out to carry out mixing and dispersion so that the nigrosine compound becomes uniform in the dispersion liquid.

The nigrosine compound used in the present invention is not particularly limited structurally, and a compound having a cation structure containing no counter anion component is preferable. Specifically, the one represented by the following equation can be used. When a conventional nigrosine charge control agent containing a counter anion such as a higher fatty acid as described above is used, it does not show reactivity with an acid group exposed on the particle surface, or an anion exchange reaction occurs, and the counter anion component is It is difficult to obtain the desired effect due to elution.

[0053]

Embedded image

[However, Ar in the formula is an aryl group. ]

Examples of the nigrosine compound include nitrobenzene, nitrophenol, nitrocresol, aniline,
It can be obtained by heating and melting and condensing aniline hydrochloride or the like as a raw material in the presence of a catalyst. When an anionic component such as higher fatty acid is contained in the production process, it is used after removing it.

Examples of commercially available products include Bontron N-0.
1, Bontron N-07, Bontron EX (all manufactured by Orient Chemical Industry Co., Ltd.) and the like can be used.

The nigrosine compound used in the present invention is added in an amount of 0.3 to 100 mol% based on the acid groups on the surface of the toner particles.
A considerable amount can be used, but more preferably 3 to 85
Addition of mol% equivalents gives good results. Within this range, the sufficient effects of the present invention can be obtained, and the characteristics of the toner particles themselves are not impaired.

The amount of acid groups on the surface of the toner particles can be determined by a titration method. For example, the concentration can be calculated by the following method. To the granulated aqueous dispersion of toner particles, an excess of 1N sodium hydroxide aqueous solution is added and thoroughly mixed with stirring to add sodium ions to the acid groups on the surface of the toner particles. Then, the aqueous dispersion of the toner particles is filtered and washed to remove excess sodium hydroxide other than those ionically bonded to the functional groups on the surface of the particles. Next, the toner particles are redispersed in water, and a 1N aqueous hydrochloric acid solution is added dropwise while stirring until the pH of the aqueous dispersion becomes 3. From the dropped amount of this 1N hydrochloric acid, the amount of sodium ions on the surface of the toner particles, that is, the amount of acid groups can be calculated. This method is suitable for measuring the carboxyl group content.

The toner particle dispersion thus obtained typically contains toner particles having a structure in which a nigrosine compound is ionically attached to the surface of the toner particles.

A dry toner can be easily obtained by removing the liquid medium and drying the thus obtained toner particle dispersion liquid. In addition, it is preferable to repeatedly perform washing in order to remove the dispersion stabilizer and the emulsifier in the dispersion liquid. In carrying out the liquid medium removal / drying step, after filtering the toner particles, it is possible to perform hot air drying or freeze drying at a temperature at which the toner does not fuse, or to remove and dry the liquid medium with a spray dryer or the like. You may make it perform simultaneously.

According to the first to third aspects of the present invention, a spherical toner having a narrow particle size distribution (monodisperse) can be obtained, but if necessary, further classification may be performed.

As the particle size of the toner powder of the present invention, any size can be selected within a practical level as a toner. The volume average particle diameter is 3 to 30 μm, preferably 4 to 12 in view of the matching property with the current machine.
The range of μm is preferable.

The electrophotographic toner of the present invention can be used as a non-magnetic one-component toner or a magnetic one-component toner, or as a two-component developer when combined with a carrier, and is particularly excellent as a two-component developer. The characteristics can be obtained.

As the carrier, any known carrier can be used, and examples thereof include iron, nickel, copper, zinc,
Powders of metals such as cobalt, manganese, chromium, rare earths and alloys or oxides thereof, surface-treated glass, silica and the like can be used. Of course, resin-coated carriers such as acrylic resin-coated carriers, fluororesin-coated carriers, and silicone resin-coated carriers can also be used. As the carrier, for example, a carrier of about 20 to 200 microns is used.

When a two-component electrostatic image developer is obtained from the toner obtained in the present invention and a carrier, the toner is mixed in a ratio of 1 to 15 parts by weight of toner per 100 parts by weight of carrier. You can use it.

[0066]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a preferred embodiment of the present invention will be specifically described with reference to an example of producing a black toner by a suspension polymerization method.

First, with the styrene-based monomer as the main component,
(Meth) acrylic acid ester, (meth) acrylic acid,
The glass transition temperature of the polymer (binder resin) after polymerization is 50.
~ 80 ° C, content of (meth) acrylic acid in all monomers 1
It is used so as to be 0 to 20% by weight and the total monomer 1
2 to 8 parts by weight of carbon black powder per 100 parts by weight, 0.5 to 3 parts by weight of azo polymerization initiator per 100 parts by weight of all monomers, 0.05 to 3 parts by weight per 100 parts by weight of all monomers Partial amount of sulfur chain transfer agent,
0.3 to 3 parts by weight of a polyolefin wax is dispersed and mixed in advance under ultrasonic vibration per 100 parts by weight of all the monomers, and water is added to the mixture to suspend the monomer droplets while stirring. Polymerization is performed at ˜95 ° C. for 3 to 8 hours to obtain a dispersion of toner particles having carbon black particles encapsulated therein and finely dispersed with a polyolefin wax and having a particle diameter of 4 to 15 μm and a carboxyl group exposed on the particle surface.

Then, to this dispersion, a nigrosine compound in an amount of 3 to 85 mol% of the exposed carboxyl groups of the toner particles is added, uniformly mixed and dispersed, and at least a part of the carboxyl groups is neutralized. After that, the toner particles are filtered out from the dispersion liquid and dried below the softening point of the binder resin forming the toner particles to obtain a toner powder.

The toner powder thus obtained is mixed in an amount of 3 to 10 parts by weight per 100 parts by weight of the carrier, and can be used as a two-component developer for electrostatic image development.

[0070]

The present invention will be described more specifically below with reference to examples of the present invention. However, the invention is not limited to these examples.

(Example 1) Methacrylic acid 45 g Styrene 207 g Butyl acrylate 30 g Methyl methacrylate 15 g Ethylene glycol monomethacrylate 3 g Azobisisobutyronitrile 6 g Dodecyl mercaptan 3 g Carbon black 15 g [Basic carbon black manufactured by Cabot, USA] Viscole 550P 3g [Sanyo Kasei Co., Ltd. polypropylene wax]

After the above mixture was dispersed by an ultrasonic homogenizer, 1500 g of ion-exchanged water was added and dispersed and suspended. This mixed liquid was placed in a flask equipped with a stirring blade, and suspension polymerization was carried out at 80 ° C. for 5 hours under a nitrogen stream to prepare an aqueous dispersion of toner particles composed of resin fine particles containing a colorant. When the toner particles were measured with a Coulter counter, they were toner particles having an average particle diameter of 8 microns. Further, it was confirmed by observation with an electron microscope that the toner particles were truly spherical. The washing operation of filtering this aqueous dispersion of toner particles and returning to water again was repeated several times.

Next, with respect to this toner particle aqueous dispersion,
"Bontron N-07" 2.3 as a nigrosine compound
9 g was added and sufficiently stirred. Then, the toner particle dispersion liquid was filtered and treated with a freeze dryer for 3 days to obtain a dry toner. This toner had excellent fluidity, and no aggregation of particles was observed.

The obtained dry toner is treated with an average particle diameter of 100.
The developer was prepared by mixing and stirring 4 parts by weight with respect to 100 parts by weight of the micron coated ferrite carrier, and the charge amount of the toner was measured by the blow-off method. As a result, it showed a value of +20.3 μC / g, showing a positive polarity. It was confirmed to be a charged toner. When a copying test was carried out using a commercially available electronic copying machine using this developer, a clear image faithful to 20,000 or more originals having a uniform image density was obtained.

Comparative Example 1 A dry toner was prepared without adding the Nigrosine compound “Bontron N-07” used in Example 1. That is, a toner was prepared in which the nigrosine compound was not ionically added to the carboxyl groups on the surface of the toner particles. Similar to the toner obtained in Example 1, this toner had excellent fluidity, and no aggregation of particles was observed. This dry toner was mixed and stirred at a ratio of 5 parts by weight to 100 parts by weight of a ferrite carrier having an average particle diameter of 100 microns to prepare a developer, which was -36.8 μC.
The charging amount was / g, and the charging amount was sufficient for practical use as a negatively charged toner. However, when the developer was prepared by mixing and stirring at a ratio of 4 parts by weight to 100 parts by weight of the coated magnetite carrier having an average particle diameter of 100 microns as in Example 1, the toner charge amount by the blow-off method was It showed a value of −8.3 μC / g, had a negative charging property as before, and could not be used as a positive charging toner.

[0076]

According to the invention of claim 1, toner particles comprising a binder resin containing a colorant and comprising an acid group-containing monoethylenically polymerizable monomer are obtained by suspension polymerization. Since at least a part of the acid groups exposed on the surface of the toner particles is neutralized with a nigrosine compound, it is compared with a positively chargeable toner produced by a conventional polymerization method in which the monomer composition and the type of the charge control agent are changed to granulate. Therefore, it is possible to easily produce a positively chargeable toner by using the same starting material as that of the negatively chargeable toner and by the same granulation process, which is caused by the dispersibility of each component and the change of the reaction rate of the monomer. The difficulty of forming uniform colorant-dispersed particles is eliminated, charge control for achieving a positive charging property is easier, and a remarkable effect is obtained in that the content of impurities is smaller than in the emulsion polymerization method described later.

According to the second aspect of the present invention, the colorant and the monomer are mixed or dispersed by ultrasonic waves, and then the colorant is included and the monoethylenic polymerizable monomer containing an acid group is contained. Since the toner particles composed of the binder resin are obtained by suspension polymerization, the essential dispersion stabilizer is not particularly required in claim 1, and the same starting material as that of the negatively chargeable toner is used and the same granulation process is used. Since it is possible to easily produce a positively chargeable toner by using, it is possible to eliminate the difficulty of forming uniform colorant-dispersed particles due to the change in the dispersibility of each component or the reaction rate of the monomer, and to make the toner positively chargeable. It is easier to control the charge and the effect is particularly remarkable, as compared with the emulsion polymerization method described later, in which the content of impurities is smaller.

According to the third aspect of the present invention, toner particles containing a colorant and comprising a binder resin composed of a monoethylenically polymerizable monomer containing an acid group are obtained by emulsion polymerization, and the toner is obtained. Since at least a part of the acid groups exposed on the surface of the particles is neutralized with a nigrosine compound, compared with a positively chargeable toner produced by the conventional polymerization method in which the monomer composition or the type of the charge control agent is changed to granulate, Since a positively chargeable toner can be easily produced by using the same starting material as the chargeable toner and by the same granulation process, a uniform colorant caused by the dispersibility of each component and the change in the reaction rate of the monomer. It is possible to obtain the remarkable effect that the difficulty of forming dispersed particles is eliminated and the charge control for making the particles positively charged is easier.

In the invention of claim 4, since a wax is used together during the polymerization, a particularly remarkable effect that a toner having a better releasability can be obtained is obtained.

In the invention of claim 5, since basic carbon black is used, a particularly remarkable effect that a toner having excellent affinity with the binder resin and more stable charging characteristics can be obtained can be obtained.

Claims (5)

[Claims] 1. A colorant, a monoethylenically polymerizable monomer having an acid group, and a dispersion stabilizer as essential components in a liquid medium in which the monomer is insoluble and insoluble in the liquid medium and Polymerization is carried out in the presence of a monomer-soluble polymerization initiator to obtain a dispersion liquid of the toner particles insoluble in the liquid medium, which is composed of a polymer of the monomer including a colorant. A method for producing an electrophotographic toner, comprising a second step of adding a nigrosine compound to neutralize the acid groups in the polymer, and a third step of removing the liquid medium from the second step and then drying. 2. A coloring agent and a monoethylenically polymerizable monomer containing an acid group as essential components, which are ultrasonically mixed to each other in the monomer-insoluble liquid medium to the liquid medium. Polymerization in the presence of a polymerization initiator insoluble and soluble in the monomer to obtain a dispersion liquid of the toner particles insoluble in the liquid medium, which is a polymer of the monomer containing a colorant. A method for producing an electrophotographic toner, which comprises a second step of adding a nigrosine compound thereto to neutralize the acid groups in the polymer, and then a third step of removing the liquid medium therefrom and drying. 3. A coloring agent, a monoethylenically polymerizable monomer containing an acid group, and an emulsifying agent as essential components are polymerized in an aqueous medium in the presence of a water-soluble polymerization initiator to obtain a coloring agent. A first step of obtaining a dispersion liquid of the toner particles insoluble in the aqueous medium, which comprises a polymer of the monomer, and a second step of adding a nigrosine compound thereto to neutralize the acid groups in the polymer, Then, a method for producing an electrophotographic toner, which comprises a third step of removing the aqueous medium and drying the resultant. 4. The production method according to claim 1, 2 or 3, wherein a wax is used together during the polymerization. 5. The method according to claim 1, 2 or 3, wherein basic carbon black is used as the colorant.